The bodies of 19 elite firefighters overtaken by a raging wildfire in central Arizona were recovered and taken to the Maricopa County Medical Examiner's Office today, Prescott Fire Chief Dan Fraijo said.

The Yarnell fire killed 19 of 20 members of the Granite Mountain Hotshot Crew, who ranged in age from 21 to 43 years old.

"That would be where you simply have no way to get to a safety zone and you realize to save your life, you're going to have to deploy the shelter," he said.

"Often, that kind of scenario means you just have very few moments left to get in your fire shelter. Nobody wants to get in one," Frederick said.

Authorities believe the wildfire began with a lightning strike Friday in Yarnell, Ariz., about 90 miles northwest of Phoenix, and spread to at least 2,000 acres Sunday amid triple-digit temperatures, low humidity and windy conditions. By early today, the Yarnell fire had tripled in size and was 6,000 acres, according to Arizona incident commander Mike Reichling.

"I said last night that my heart was breaking. I can't even imagine how the friends and families feel," Arizona Gov. Jan Brewer said at a news conference today. "It's unbearable for many of you, but it's is unbearable also for me.

"For now, we mourn. Consider this: The fire claimed more lives than any single disaster since 9/11," an emotional Brewer said. "Just as we remembered the brave men who ran into the twin towers, we will also remember the men of the Granite Mountain Hotshots."

Fire shelters became mandatory safety equipment in the 1970s and have been used ever since. The devices are made of fiberglass and aluminum that together create "basically a personal tent," Frederick said.

"During a fire entrapment, a firefighter can take it out if its case, flap it open and then crawl underneath it," he said. "What it does is reflect away radiant heat and trap cool, breathable air for the firefighter."

Firefighters are trained to be able to deploy the shelter in about 30 seconds, Frederick said, adding that they have saved hundreds of lives.

If at all possible, Frederick said, a firefighter would rather use an escape route to get to a safety zone than have to get out the fire shelter. He was a firefighter for 13 years in Washington and never even took out his fire shelter, much less deployed it.

Unfortunately, the shelters do have limitations. They cannot withstand prolonged extreme heat, which can cause the aluminum to delaminate from the fiberglass. A wind event similar to what officials believe may have occurred in Yarnell, combined with hot, dry and windy conditions, can be a worst-case scenario for even the most experienced firefighter.

"You base your actions on what the fire is doing and what you expect it to do, but if that changes rapidly and unexpectedly, that's the worst kind of situation for a firefighter," Frederick said.

The 19 deaths amounted to the greatest loss of life for firefighters in a wildfire since 1933 when the Griffith Park fire in southern California claimed the lives on 29 firefighters, according to the National Fire Protection Association.

It is also the deadliest day for U.S. firefighters since 9/11, when 340 died.

"Hotshot" crews are elite firefighters who often hike for miles into the wilderness with chain saws and backpacks filled with heavy gear to build lines of protection between people and fires. They remove brush, trees and anything that might burn in the direction of homes and cities.

"They're not the people that have engine companies and large trucks. These are the core of firefighting where they're right there in the middle of the incident," Fraijo said at a Sunday night news conference.

Fraijo said the crew killed in the Yarnell fire worked other wildfires in recent weeks in New Mexico and Arizona.

He added that the firefighters had to deploy the tent-like structures when "something drastic" occurred.

"One of the last fail-safe methods that a firefighter can do under those conditions is literally to dig as much as they can down and cover themselves with a protective -- kind of looks like a foil type, fire-resistant material -- with the desire, the hope, at least, is that the fire will burn over the top of them and they can survive it," Fraijo said.

The Prescott-based crew never had to use shelters during a wildfire, according to a 2012 profile in a Cronkite News Service report.

Reichling, the incident commander, said half of the 500 structures in Yarnell have been destroyed by the "radical weather." Most of Yarnell's 700 residents have been forced to evacuate.

"We have fires throughout the state right now. We have the winds that change. That's what happened today and caused this tragedy," he said.

Evacuee Don Mason said, "I don't know if my home's standing or not, but from what I've heard, most of Yarnell has burned to the ground. So it's been tough."

About 200 firefighters are fighting the wildfire, which has also forced the closure of parts of state Route 89. None of the fire is contained.

President Obama, who is traveling in Africa, released a statement early this morning, calling the 19 firefighters "heroes" for putting "themselves in harm's way to protect the lives and property of fellow citizens they would never meet."

Former U.S. Rep. Gabrielle Giffords expressed her shock on Twitter, calling the death of the firefighters "absolutely devastating news."